1. Field of the Invention
The present disclosure relates to a portable storage apparatus and method, and more particularly, to a portable storage apparatus and method for changing a data bus width.
2. Description of the Related Art
Generally, a portable storage apparatus is used in a digital apparatus, such as in a camcorder, a digital camera, a personal digital assistant (PDA), an MPEG-1 Layer 3 (MP3) player, and the like. A portable storage apparatus typically includes a MultiMediaCard (MMC), secure digital (SD) memory card, CompactFlash (CF) Card, memory stick, or other storage media. An example of a conventional memory card is disclosed in U.S. Pat. No. 6,446,163.
A portable storage apparatus has multiple data bus widths. The data bus width in the portable storage apparatus is changed in accordance with a current host to which the apparatus is connected in order to accommodate data communications for hosts having different data bus widths. Thus, a conventional portable storage apparatus includes a predetermined register in which data bus width information is stored. The data bus width in the portable storage apparatus is preset by the host when the portable storage apparatus is connected to the host. Such a conventional portable storage apparatus will be explained with reference to FIG. 1.
FIG. 1 is a block diagram illustrating a conventional portable storage apparatus in signal communication with a host. As shown in FIG. 1, a portable storage apparatus 2 includes a command pin P1 for receiving a command packet, electric power source pins P2 and P3, a clock signaling pin P4, and a plurality of data pins D1 through DN. The command pin P1, the electric power source pins P2 and P3, the clock signaling path P4, and the plurality of data pins D1 through DN are respectively connected to a host 1. In addition, the portable storage apparatus 2 further includes a command packet decoder 30, a control unit 40, a first register 50, a flash memory 60, a data buffer 70, and a second register 80. The command packet decoder 30 includes a packet receiving unit 31, a command field decoder 32, and an argument field decoder 33. The packet receiving unit 31 is connected to the command pin P1 through a command line 10, and the control unit 40 is connected to the data buffer 70 through a plurality of data lines 20.
A process of setting a data bus width in the portable storage apparatus 2 having the above structure will be explained. If the portable storage apparatus 2 is connected to the host 1, the host 1 transmits a command packet CMD_PK for setting the data bus width. The packet receiving unit 31 of the command packet decoder 30 receives a command packet CMD_PK through the command line 10 and divides the received command packet CMD_PK into a command field CMD_FD and an argument field ARG_FD. The command field decoder 32 outputs command information CMD_IF by decoding the command field CMD_FD. The argument field decoder 33 outputs data bus width information BUS_IF by decoding the argument field ARG_FD. The control unit 40 receives the command information CMD_IF and recognizes this information as a command for setting the data bus width. Furthermore, the control unit 40 receives the data bus width information BUS_IF and stores it at a first register 50. Thereafter, the control unit 40 transmits and receives data by selecting all or some of the plurality of data lines 20, based on the data bus width information BUS_IF. Moreover, the command field decoder 32 outputs a write or a read command by decoding the command field CMD_FD when transmitting and receiving general data. The argument field decoder 33 outputs an address signal by decoding the argument field ARG_FD when transmitting and receiving the general data.
Therefore, the data bus width is set before any data bus communication with the host in the conventional portable storage apparatus. This conventional method is only useful for a case where there is no need to change the data bus width for a long period of time, that is, when the portable storage apparatus is connected to only one host. However, if the data bus width is required to change frequently, such as when the portable storage apparatus is connected to several hosts, the data bus width is reset in advance whenever the host is changed. Accordingly, the host must separately transmit the command packet for setting the data bus width in advance, and furthermore, the data bus width is reset whenever the host is changed in the conventional portable storage apparatus.